Orange-fronted parakeets (Cyanoramphus malherbi) are New Zealand’s rarest parakeet species with a global population of less than 500 individuals on remnant mainland populations and reintroduced populations on offshore islands. Since there is limited information about habitat preferences by this species on offshore islands I characterised habitat use on Maud Island, where captive-bred parakeets were introduced in 2007. I compared the vegetation characteristics of 29 plots (each 25 m2) where parakeets were encountered and 23 plots randomly selected. Parakeets were observed foraging in 96.6% of the plots. Plots used by parakeets showed significantly higher density of stems under 20 cm dbh and a higher canopy than random plots. Used plots also tended to have greater canopy cover and lower understory and ground vegetation covers. These results indicate that orange-fronted parakeets use ecotones of broadleaf coastal forest-manuka scrub, and pine plantations-manuka scrub for foraging highlighting the potential value of islands with mixed patches of these vegetation types as future refuges for this critically endangered species.
The diet of the Australasian gannet (Morus serrator) at Farewell Spit, New Zealand, was studied by the analysis of 70 regurgitations collected from the 1995 to 2001 breeding seasons. Surface schooling pilchard (Sardinops neopilchardus) was the main prey, followed by anchovy (Engraulis australis). The composition of the diet was similar in most seasons examined except in 1996 in which anchovy was the main prey item. Such a change in diet could be linked with a pilchard mass mortality in New Zealand in August 1995. The estimated annual prey consumption by birds at the Farewell Spit gannetry was 852 tonnes. Although annual catches of pilchard and anchovy by commercial fisheries in the area are still relatively small, an increase may interfere with prey availability, and in turn, increase competition between marine predators and influence the breeding success. Our analyses of diet are consistent with previous studies showing that Australasian gannets as flexible foragers and they highlight their importance as bioindicators of fish stocks in New Zealand.
The New Zealand endemic red-billed gull (Larus novaehollandiae scopulinus) was designated as a ‘Nationally Vulnerable’ species in 2008 as a consequence of recent substantial population declines at large breeding colonies, particularly the one situated at Kaikoura, north-east South Island. In contrast, numbers increased further south along the Otago coastline, south-east South Island. Nest numbers from 7 surveys from Moeraki to Nugget Point increased from 565–1480 in 1992 to 4612–4652 in 2011 and corresponded to an average annual increase of 6–10% through 20 years. The recent decline at Kaikoura has been attributed mainly to a decline in prey availability linked to changes in oceanographic indicators, including sea surface temperature (SST). Fluctuations in SST at Otago and Kaikoura are negatively correlated and may explain the concomitant opposite trends in population sizes. Conservation management at Taiaroa Head and at other key mainland breeding locations is necessary to ensure the viability of red-billed gulls at Otago.
The Marlborough Sounds has a coastline of 1500 km and hosts the greatest diversity of marine shag species in New Zealand. A survey of all breeding shag species was conducted in spring 2006. Apart from New Zealand king shag, 3 species were counted: spotted shag (Strictocarbo punctatus), pied shag (Phalacrocorax varius) and little shag (Phalacrocorax melanoleucos). Two other species (black shag Phalacrocorax carbo and little black shag Phalacrocorax sulcirostris) also occur in the area but were not recorded breeding. A total of 1,254 pairs of spotted shag were recorded at 193 sites, with most colonies occurring in the outer Sounds and inner Queen Charlotte Sound. Average colony size was 6.5 pairs (range 1-76 pairs), with 85% of colonies containing ≤10 pairs. The distribution of spotted shag colonies appears to be influenced by the availability of suitable cliff habitat. Breeding pied shags were found at 48 colonies, with a total of 438 pairs. Colonies were widely distributed, and average colony size was 9.1 pairs (range 1-28), with 83% containing ≤15 pairs. A total of 226 little shag pairs were found at 24 colonies, with most colonies also including nesting pied shags. Colony size was on average 9.4 pairs (range 4-24), with 75% of colonies containing ≤10 pairs. Colonies of pied shags and little shags were found mostly in native vegetation. Colonial seabirds that occur at relatively few locations can be used as indicators to establish critical thresholds for marine management and marine conservation. It is proposed that this survey provide a good baseline for such an approach in the Marlborough Sounds.
Diagnostic prey remains of Auckland Island shags (Leucocarbo colensoi) were analysed from 23 regurgitated pellets collected in August 2010 at Enderby Island, Auckland Islands. Allometric equations from a reference collection were applied to prey remains to provide estimates of prey length and wet mass. A minimum total of 1058 prey items from 7 genera were represented in pellets, with an estimated total wet mass of 13.2 kg. The mean number of prey items per pellet was 46 (range 7-90), with mean total prey mass per pellet of 589 g (range 86–1037 g). Small octopus (Octopus sp.) was by far the most important prey item and was present in all regurgitated pellets. It accounted for 57% of prey by number and 68% of prey by wet mass. Only 2 other genera contributed ≥ 5% towards the total mass of prey—red cod (Pseudophycis bachus) and triplefin (Forsterygion sp.) The overwhelming importance of octopus in the diet is unprecedented among shags for which diet composition is known.
Stable isotopic (δ13C; δ15N) analysis of bone collagen and other refractory biological materials is a mainstay of palaeoecological research, but comparability between individuals depends on homogeneity within the sample specimens. Long bones of extinct New Zealand moa display lines of arrested growth that reflect prolonged development over several years, leading to potential systematic inhomogeneity in stable isotopic enrichment within the bone. We tested whether the isotopic content within a Euryapteryx curtus tibiotarsus is homogeneous by measuring δ15N and δ13C values in 6 adjacent 1cm-diameter cortical bone cores arranged along the bone axis from each of the proximal and distal ends. We then measured isotopic ratios in 5 radial slices of a core from the mid-shaft of a Pachyornis elephantopus tibiotarsus to see if there was any depth (ontogenetic) effect at a single sampling point. The δ13C value increased with distance from the proximal bone end, but neither δ13C nor δ15N values in samples from the distal end of the bone were correlated with position. Within mid-shaft cortical bone, the δ13C value decreased with depth but δ15N values were constant. Sampling the entire depth of cortical bone from the caudal surface at the distal end of the tibiotarsus, if feasible, therefore provides a spatially homogenous material, free of maturation effects on stable isotopic composition. If for any reason that position cannot be sampled, the outer (radial) layer at the mid-shaft can be substituted.
The introductions of mallard (Anas platyrhynchos) to New Zealand, and their breeding and release as a game bird by Acclimatisation Societies are summarised. We identify 19 importations, 14 of which (a total of 115 birds all from Great Britain) were sufficient to establish small feral populations in southern and central New Zealand by about 1910. Five subsequent importations were made by Aucklander C.A. Whitney, 3 from Great Britain in 1910 (6 birds), 1914 (number unconfirmed) and 1927 (393 birds), followed by 99 birds (1937) and 45 eggs (1941) both from the USA. It was Whitney’s distribution of eggs following his initial USA importation that prompted widespread breeding and release programmes which, in some regions, extended into the 1960’s and 70’s. We identify a minimum of 30,000 mallards having been released by Acclimatisation Societies, but numerous releases by private individuals remain unrecorded. Almost all regional Acclimatisation Societies at some time released mallards into the wild.